1. Field of the Invention
The present invention relates to an electrical power supply apparatus, especially for a motor vehicle electrical system.
2. Description of Related Art
One of the problems encountered with alternators which feed the electrical systems of motor vehicles lies in the fact that they are driven by the heat engine at variable speeds of rotation.
The performance of these alternators consequently varies according to the running mode of the engine, whereas the electrical system would require to be fed at constant power.
In order to overcome this drawback without prohibitive increases in weight, size and cost of the generator, various apparatuses have been proposed.
All of these are based on one of the two following principles:
driving of the alternator through a variable ratio device.
double alternators or an alternator with double three-phase windings, connected in series at low running modes of the engine and in parallel at high running modes of the engine.
The arrangements known at this time remain complex and expensive, or else they have reduced performance.
One object of the invention is to overcome these disadvantages.
To this end, it proposes an electrical power supply apparatus, especially for a motor vehicle electrical system, comprising at least two power supply sources which are both connected between ground and a supply line, and each of which comprises at least one induced current winding and a bridge of rectifier elements, characterised in that one of the two said sources comprises an auxiliary bridge of rectifier elements of positive type, the other one comprising an auxiliary bridge of rectifier elements of negative type, with means, connected to each of the said two bridges and being adapted to be controlled for the purpose of:
in a first state, connecting the two auxiliary bridges in series, the rectified voltage supplied to the power supply line then being the sum of the voltages supplied by the induced current winding or windings of each of the two sources and then rectified,
in a second state, blocking the connection between the two auxiliary bridges, the two sources then supplying the power supply line in parallel.
Such an apparatus is preferably completed by the features as set out as follows:
the two sources are three-phase sources;
a control means is a controllable interrupter interposed between the two auxiliary bridges;
a control means is a controlled diode interposed between the two auxiliary bridges;
a control means is a transistor of CMOS type, interposed between the two auxiliary bridges;
a control means comprises control diodes which constitute rectifier elements of one and/or the other of the two auxiliary bridges;
the diodes of the two auxiliary bridges are carried by a common support;
the two sources are two alternators on which the two auxiliary bridges are respectively mounted;
the two sources are synchronous sources, the rectifier elements of the two auxiliary bridges being connected in pairs and providing the connection between the phases of the two corresponding sources, the branches connecting two rectifier elements of each of the two auxiliary bridges being connected in pairs by means constituting an interrupter, these interrupter means constituting the control means;
the two sources are synchronous three-phase sources, and in that the control means comprises at least one double interrupter;
the induced current windings consist, respectively, of a delta connected induced current winding and a star connected induced current winding;
the delta connected induced current winding has a number of turns per slot which is equal to the number of turns per slot in the star connected induced current winding multiplied by the square root of the number of phases in the electrical machine.